Some processors have larger access sizes to simplify the hardware. The
first DEC Alpha, and some ARM designs, had no instructions for reading
or writing 8-bit or 16-bit data. In effect, these had 32-bit (maybe on
the Alpha it was 64-bit) "byte" sizes. But smaller access sizes could
be easily simulated in software.
Machines not so well designed require masking off the appropriate
bits before operating with them, though many machines ignore high
bits on shift operations. (The 8086 allows shifts up to 255 bits.)
On 2020-02-28 09:23, gah4@u.washington.edu wrote:
Machines not so well designed require masking off the appropriate
bits before operating with them.
Who can say that the CDC machines (7600; 70 series, etc) were not
well designed?
They were intended to be fast, and to carry out operations on
words (of 60 bits).
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